After a couple of years of happily using the google play store / market on my android devices, the ability to download applications suddenly stopped...
Talking to my ISP & then HTC did not result in a solution, although I had narrowed it down to being a router issue (I could use the play store if connected to other wifi networks).

A little googling unearthed this forum thread:
http://forums.whirlpool.net.au/archive/1840357
Which produced a working solution, albeit odd. The nub of the solution being to manually input DNS addresses into the router configuration.
Those suggested on the forum were Primary 8.8.8.8, Secondary 8.8.4.4
I've yet to play further, but once I dig out my ISP DNS I will...

However, I thought I would post this here, in case others were having the same issue, and in case someone from Draytek could shed further light on the issue.

LC2